Since the advent of the powered wheel, man has relentlessly searched for means to enhance the traction of the wheel with the surface upon which it operates. Early on, the wide steel driving wheels of stem powered traction machinery were equipped with massive steel lugs which bit into the earth and gave the wheel the traction required to pull a number of breaking or turning plows through the earth. The wide wheels were necessary to provide the area required to support the tractor and prevent its _great weight from causing it to sink into the earth, while the lugs provided the grip in the soil required to pull the plows. The coming of the horseless carriage created an entirely new set of problems, as it was nothing more than a motorized adaptation of a horse-drawn vehicle, having free-turning wheels, which were meant to be pulled across the earth, rather than propelled by the powered rotation of the wheels. It was soon discovered that the steel band, or tire, that encircled the wooden wheel rims, was only suitable for use on hard-packed and tinder-dry surfaces and from this discovery there evolved the wider solid rubber and then the pneumatic tire. Since the evolution of the pneumatic tire, great effort has been dedicated in the search for means to improve the traction of the driving wheels of all manner of vehicles upon the surface and under the conditions which they must operate. Water, mud and snow are three of the most difficult conditions to address with a modern vehicle tire. Each of these conditions requires a specific tire tread suited either to channelize the water away from the tire or grip the soft or slippery surface and either bring more material under the tread area or compact the material to provide a suitably stable driving surface. These conditions however, pale by comparison with the problems encountered when operating a wheeled vehicle on an ice covered surface. No amount of tread, ribs, bars or other such means are effective upon a surface of solid ice. While time-honored detachable tire chains or cleats provide a measure of traction under these conditions, their use has never been popular due to the difficulty of installation and removal and the bone-shaking ride which they impart to a vehicle employing them.
In an attempt to solve these problems the "studded tire," which comprises a tread area which includes a number of hard stud-like projections which extend a short distance beyond the face of the tread to slightly penetrate the surface of the ice and thereby provide a limited mount of traction between tire and roadway, was developed. While it appeared that the studded tire would be the definitive solution to the operation of a vehicle on an ice covered surface, such was not the case. Soon after the introduction of studded tires, street and highway officials began to detect rapid deterioration of street and roadway surfaces and called for legislation to restrict their use. Today, in most states and municipalities, the use of the studded tire is controlled by law, ordinance or regulation requiring that such tires be used only during certain winter months and that they be removed from service during the warmer months. Unfortunately, some states, notably Hawaii, Illinois, Louisiana, Michigan, Minnesota, Mississippi and Wisconsin have enacted legislation which prohibits their use at any time and have thus deprived motorists of the safety and convenience advantages that they provide. The reasons for such regulations are obvious however, as tungsten steel studs are of a hardness greater than the surface of even the most durable of roadways and are capable of chipping away at the concrete with each revolution of a vehicle's wheels. Mother factor which has to some extent lessened the popularity of the studded tire is the fact that the protruding stud reduces, to a certain degree, the ability of the tire to grip a dry roadway with a consequent diminution of braking action. Also, the rotation of the studded tire upon a dry roadway causes an undesirable noise and vibration inside the vehicle and finally, the requirement for removal of studded tires during the warmer months and their re-installation for the winter requires either a second set of wheels for each vehicle or the semi-annual removal and replacement of the tires upon the same wheels with the consequent potential for damage to the "bead" or air sealing area of the tire. Of lesser importance, but still a factor affecting their popularity, is the requirement for storage space for the second set of tires when they are out-of-service.
In the more temperate areas of the nation the requirement for ice studs is virtually non-existent or may be limited to only a few as a days a year and quite possibly only for a portion of those days. For example, in the United States, regions south of the 31st parallel, except in the higher elevations, are seldom subject to climatic conditions which produce freezing rain and the consequent coating of ice which makes studded tires necessary. Conversely, the area north of the 36.degree.-30' parallel is likely to have ice, snow or a combination of both on the ground for many days or even weeks. The area between these two parallels may have an ice storm overnight which may result in almost impossible driving conditions during a morning commute, while the evening commute may be made on dry, or nearly dry, roadways.
In order to accommodate the differing requirements of various geographical and climatic regions a number of inventors have attempted to solve these problems by providing tires with retractable traction enhancing elements. Examples of these earlier attempts are illustrated in the prior art in the following disclosures. Lowry, in U.S. Pat. No. 2,217,122 disclosed an "Anti Skid Tire" having two substantially concentric casings which are selectably inflatable or deflatable to cause the extension or retraction of stud-like anti-skid projections. Anderson in U.S. Pat. No. 3,672,421 similarly disclosed a method whereby stud-like projections are forced through the tread area of a tire by differential air pressure between the interior of the cuing and hoses which pass about the inner periphery of the casing and pass under staple-like retractable studs. Einarsson in U.S. Pat. No. 3,872,908 employs a similar differential air pressure system for extending and retracting studs through the tread area of a tire and provides an internal receiver for high pressure actuating air within the casing and a specialized valve for filling said reservoir and extending or retracting the studs. Crandall in U.S. Pat. No. 3,942,572 employs a multi-chambered cuing which allows the pneumatic outward flexure, into roadway contact, of a centrally situated stud-bearing band about the periphery of the tire at the center of the tread band.
While it is not the intention of this applicant to derogate the objectives of these inventors, or be critical of their efforts, it is obvious that none were familiar with the, then and now, gate-of-the-art of tire manufacturing technology and as a consequence, these inventions have not been adopted by the industry and have thus been relegated to obscurity.